Communication systems are known to transport large amounts of data between a plurality of end user devices. Such end user devices include telephones, facsimile machines, computers, television sets, cellular phones, personal digital assistants, et cetera. As is also known, such communication systems may be a local area network (LAN) and/or a wide area network (WAN). A local area network is generally understood to be a network that interconnects a plurality of end user devices distributed over a localized area (e.g., up to a radius of 10 kilometers) and includes LAN infrastructure equipment. For example, a local area network may be used to interconnect workstations distributed within an office of a single building or a group of buildings, to interconnect computer based equipment distributed around a factory or hospital, et cetera. As is further known, local area networks may be wired local area networks or wireless local area networks. Wired local area networks typically have a star topology, ring topology, bus topology or hub/tree topology.
A wide area network is generally understood to be a network that covers a wide geographic area and includes WAN infrastructure equipment. Wide area networks include both public data networks and enterprise wide private data networks. A public data network is established and operated by a national network administrator specifically for data transmission. Such public data networks facilitate the inner working of equipment from different manufacturers. Accordingly, standards by the ITU-T have been established for conveying data within public data networks. Currently, there are two main types of public data networks: packet switched public data networks and circuit switched public data networks. For example, the public switched telephone network is a circuit switched public data network while the Internet is a packet switched public data network. Other examples of wide area networks include integrated service digital networks (ISDN) and broadband multiservice networks.
As is further known, communication systems may be networked together to yield larger communication systems, where such networking is typically referred to as internetworking. Internetworking is achieved via internetworking units that allow communication networks using the same or different protocols to be linked together. The internetworking units may be routers, gateways, protocol converters, bridges, and/or switches.
Regardless of the type of communication system (e.g., LAN, WAN, or internetworking system), each communication system employs a data conveyance protocol to ensure that data is accurately conveyed within the system. In general, a protocol is a formal set of rules and conventions that govern how system devices (e.g., end user devices, LAN infrastructure equipment, WAN infrastructure equipment, and/or internetworking units) exchange data within the communication system. Such protocols typically include regulations on receiver sensitivity (i.e., how noisy a received signal may be and how small its amplitude may be) for signals received by a system device or within a system device, and on transmit power of a signal from one system device to another or within the system device.
As is further known, each system device may process millions of bits of data per second or more. Accordingly, each system device includes high-speed data interfaces to input and output data efficiently. Such interfaces are typically implemented as integrated circuits that are mounted on a printed circuit board. A group of printed circuit boards may be mounted on a backplane and multiple backplanes may further be placed in a rack to make up the system device.
In an effort to meet the ever-increasing challenges of improving data conveyance speed, each system device includes an increasing number of integrated circuits, printed circuit boards (PCBs), and/or racks. Typically, the racks and PCBs are coupled together using coaxial cables, fiber optics, connectors, and/or wires. The integrated circuits on a printed circuit board are operably coupled together via copper traces (e.g., FR4 connections). As the number and complexity of the system devices increase, the distance between ICs, PCBs, and/or racks is increasing and is more diverse. For instance, some communication channels between ICs, PCBs, and/or racks may have one type of termination requirement (e.g., 50 Ohm DC coupling to VDD, VSS, or a mid-supply voltage), while others have a different type of termination requirement (e.g., 50 Ohm AC coupling).
To accommodate for the various types of channel termination, the termination had to be done off chip, i.e., the components that provide the termination are on the PCB. This requires additional components on the PCB and makes using an integrated circuit more complicated. It further increases the cost of the PCB.
Therefore, a need exists for programmable receiver termination network for use within receiver sections of high-speed data interfaces.